PTFO 8-8695 (CVSO 30) is a star in the 7-10 million year old Orion-OB1a
cluster that shows brightness dips that resemble planetary transits. Although
strong evidence against the planet hypothesis has been presented, the
possibility remains debated in the literature. To obtain further clues, we
inspected data from the NASA Transiting Exoplanet Survey Satellite (TESS) and
the ESA Gaia mission. The Gaia data suggest that PTFO 8-8695 is a binary: the
photometric data show it to be overluminous with respect to members of its
kinematic group, and the astrometric data are inconsistent with a single star.
The TESS light curve shows two different photometric periods. The variability
is dominated by a sinusoidal signal with a period of 11.98 hr, presumably
caused by stellar rotation. Also present is a 10.76 hr signal consisting of a
not-quite sinusoid interrupted by hour-long dips, the type of signal previously
interpreted as planetary transits. The phase of the dips is nearly 180$^circ$
away from the phase of the originally reported dips. As noted previously, this
makes them difficult to explain as planetary transits. Instead, we believe that
PTFO 8-8695 is a pair of young and rapidly rotating M dwarfs, one of which
shows the same “transient-dipper” behavior that has been seen in at least 5
other cases. The origin of these transient dips is still unknown but likely
involves circumstellar material.

PTFO 8-8695 (CVSO 30) is a star in the 7-10 million year old Orion-OB1a
cluster that shows brightness dips that resemble planetary transits. Although
strong evidence against the planet hypothesis has been presented, the
possibility remains debated in the literature. To obtain further clues, we
inspected data from the NASA Transiting Exoplanet Survey Satellite (TESS) and
the ESA Gaia mission. The Gaia data suggest that PTFO 8-8695 is a binary: the
photometric data show it to be overluminous with respect to members of its
kinematic group, and the astrometric data are inconsistent with a single star.
The TESS light curve shows two different photometric periods. The variability
is dominated by a sinusoidal signal with a period of 11.98 hr, presumably
caused by stellar rotation. Also present is a 10.76 hr signal consisting of a
not-quite sinusoid interrupted by hour-long dips, the type of signal previously
interpreted as planetary transits. The phase of the dips is nearly 180$^circ$
away from the phase of the originally reported dips. As noted previously, this
makes them difficult to explain as planetary transits. Instead, we believe that
PTFO 8-8695 is a pair of young and rapidly rotating M dwarfs, one of which
shows the same “transient-dipper” behavior that has been seen in at least 5
other cases. The origin of these transient dips is still unknown but likely
involves circumstellar material.